1. Technical Field
The invention relates to tapered metal container bodies such as used for food and beverages, and in particular to a tapered metal container body providing nesting or stacking thereof for economies of transportation. More particularly, the invention relates to such a method and apparatus for forming tapered metal container bodies from a metal strip formed of a harder and thinner material than heretofore used for forming such container bodies resulting in reduced cost.
2. Background Information
It is well known in the container forming art to form two-piece metal containers, that is, containers in which the walls and bottom of the containers or container bodies are a one-piece member and the top or end closure is a separate piece, wherein the members are formed by stamping disc-shaped blanks from a strip of metal and then subsequently drawing and redrawing the metal into the desired configuration from the metal blank.
These two piece containers have found great acceptance in the can industry and are used for a vast number of food products and beverages. The container bodies in many manufacturing operations, as well as the top end closures, are generally formed at a location distant from the food processing or beverage plant and are shipped to remote sites for subsequent filling with the end product. Small top end closures are generally flat. A great number can be shipped in relatively small volume containers. However, the container bodies occupy a relatively large space, most of which is unused space in the interior of the container body. This results in substantial shipping costs. Therefore, to reduce the shipping cost, container bodies have been tapered so they can be placed in a nested relationship enabling a considerable greater number of container bodies to be shipped in the same space heretofore required for a considerably less number of non-nested container bodies. This nesting problem is addressed and examples of such nestable containers are shown in U.S. Pat. Nos: 3,814,040; 4,366,696; and 4,503,702.
These container bodies which include the heretofore common straight cylindrical sidewall configuration or the newer tapered sidewall configuration, are mass produced in quantities of millions. Thus, a savings of only a fraction of a cent per container can save the can manufacturer and food processor a considerable amount of money. Therefore, it is desirable to form the container with as lightweight of metal as possible to reduce material cost without sacrificing the integrity of the formed container. However, it has been found that it is difficult to form tapered metal containers with a uniform sidewall thickness without wrinkling of the container body during draw and redraw operations. One method of reducing this wrinkling problem is described in U.S. Pat. No. 4,503,702 wherein the blank is first drawn to a cup having an axial height of approximately one-half the axial height of the final container, afterwhich this container is then redrawn to its full axial length with the desired taper being formed therein during the redraw. Although this method and the apparatus therefor is believed satisfactory, it still requires that the metal blank have a certain thickness in order to maintain container integrity.
Thus, the new method and apparatus of the present invention provides the same nesting features and advantages as that of the above discussed prior art, but which enables a thinner material to be utilized for forming the container by using a material with a greater hardness than heretofore used for such container body manufacture.